Waferboard lumber

ABSTRACT

Substitute lumber pieces having strengths and densities substantially equivalent to lumber are cut from single layer panels of over about 1 and normally less than 4 inches thickness made from wood wafers. The wafers are oriented with their lengths having a mean deviation to the longitudinal length of the panel measured in the major plane of the panel in the range of 0 to 10 degrees and a mean deviation measured in a minimum longitudinal plane perpendicular to the major plane from 0 to about 5 degrees and have an average effective length of at least 8 inches (200 mm), and preferably an average thickness less than 0.15 inches (4 mm) and a width of at least 0.25 inches (6 mm). Lumber is made by cutting the panel longitudinally. Preferably the panels are formed to have a substantially uniform density profile throughout their thicknesses.

This application is a continuation-in part of application Ser. No.829,564, filed Feb. 14, 1986 (which in turn is a continuation ofapplication Ser. No. 723,641, filed Apr. 16, 1985 now abandoned) nowissued as U.S. Pat. No. 4,610,913.

FIELD OF THE INVENTION

The present invention relates to waferboard lumber, more particularlythe present invention relates to lumber products formed from wafersoriented to be substantially parallel to the longitudinal axis of thelumber product and a method of producing such product.

BACKGROUND OF THE PRESENT INVENTION

There have been many patents issued and many papers published on themanufacture of lumber-like products from wood particles. Similarly it iscommon practice to manufacture wafefboard-type panel products from woodparticles and there have been a number of articles published.

In the realm of oriented strandboard, the normal practice has been tomanufacture a board from particles having a maximum length of up toabout 4 inches (100 mm) and many papers and articles have been publishedadvocating 4 inches (100 mm) as a maximum length of wafer.

However, in the recently issued U.S. Pat. No. 4,610,913, issued Sep. 9,1986 and of which this application is a continuation-in-part, advantagescan be obtained utilizing long wafers in forming a layered waferboardproduct.

Australian patent No. 136,844 issued Mar. 28, 1950 is one of the earlierdisclosures relating to the manufacture of lumber from particles. Inthis patent the particles recommended are sticks, twigs, etc that areoriented in the longitudinal direction of the lumber and securedtogether. It has also been proposed in Czechoslovakian patent number93,154 issued Dec. 15, 1959 to Stofko, to produce a moulded product byorienting wood elements in what are broadly defined as profiles such asI, U, T, L and others including pipes and windows, and pressing toconsolidate into a finished or semifinished product. The teachings ofthis patent are further applied by articles published by Stofko inDrevarsky Dyskum 2 No. 1:81-102 (1957); Drevarsky Dyskum 5 No 2:241-261(1960); Drevarsky Dyskum 2:127-148 (1962) and Drvna Industriaja 21(6):104-107 (1970). In these articles Stofko discusses panel productsand lumber products presumably moulded as taught in his patent andemphasizes the importance of slenderness ratio, i.e. the ratio of lengthto thickness of the wood particles to obtain the desired structuralproperties at an acceptable density.

U.S. Pat. No. 3,164,511 issued Jan. 7, 1965 to Elmendorf discloses themanufacture of a lumber product from wafers having length of up to about6 inches (150 mm), width up to about 1/4 inch (150 mm) and thicknessesbetween 0.005 to 0.02 inches (0.1 to 0.5 mm). To applicant's knowledgeno commercial lumber products utilizing such wood particles have beenmanufactured and sold.

U.S. Pat. No. 3,956,555 issued May 11, 1976 to McKeen describes themanufacture of a laminated beam from a combination of oriented andrandom wood particles in a press by laying alternative strips oforiented and random particles and then consolidating under pressure toform a panel and splitting the oriented strips to divide the panel in tostructures having end side sections that are oriented and would functionsimilar to flanges of an I beam interconnected by a random orientedsection that would function as the web of an I beam. This is arelatively complicated structure with limited strength and suitable onlyfor use with the products oriented to be loaded perpendicular to thesplit faces.

As far as applicant is aware, the product described in U.S. Pat. No.4,061,819 issued Dec. 6, 1977 to the present inventor describes the onlycommercially viable suitable lumber product formed from wood particles(strands). This patent teaches the use of relatively long strands toobtain structural products having physical characteristics includingdensity and strength characteristics similar to, and in some casesbetter than, those of the natural wood product it replaces.

U.S. Pat. No. 4,122,236 issued Oct. 24, 1978 to Holman describes anartificial lumber product moulded from splinters having a length of therange of about 2 to 10 inches.

Generally when waferboards (panels) or the like are made, the densityprofile through the panel is such that the skins of the panel havemaximum density and the core has the least density. States another way,the strength of the skins of the panel is higher than the strength ofcore, however, since panels are normally used with the core extendingalong the neutral axis of the bending moment such a density distributionis not a major factor in determining bending strength. It is known thatthe rate of pressure application in a press can be used to change thedensity profile through the thickness of the panel. Also in a continuouspressing operation the rate of temperature rise coordinated with therate of pressure application can be used to change the density profilewith thickness to the panel.

It is economical to product wafers since the wafers are normallyproduced by a blade having spaced edges equal in length to the length ofthe wafer to be produced cutting substantially parallel to the grain. Insome cases flat blades cutting parallel to the grain are used withspaced spurs cutting perpendicular to the grain to define the length ofthe wafers. Wafers so produced are generally relatively thin and have awidth many times greater than their thickness (thickness beingdetermined by the depth of cut of the blade and the width beingdetermined by the deflection of the cut wafer by the breaker bar of theknife).

BRIEF DESCRIPTION OF THE PRESENT INVENTION

It is an object of the present invention to provide a lumber productformed utilizing waferboard technology and wafers having the followingaverage geometry; length at least 8 inches (200 mm) maximum thickness of0.15 inches (4 mm) and a width of at least 0.25 inches (6 mm) to providea relatively inexpensive lumber product having physical characteristicssimilar to or better than those obtained from lumber made from the samespecies as the wood flakes.

Broadly the present invention relates to a waferboard lumber product anda method of making same, said waferboard lumber product comprisingdiscrete lengths of lumber having thicknesses of at least 1 inch (25 mm)made from a single layer panel formed from wood wafers, said wafersbeing oriented to have their lengths orientated to the longitudinallength of the panel measured in the major plane of said panel with amean deviation of 0 to 10 degrees and a mean deviation measured in aminor longitudinal plane through the panel perpendicular to the saidmajor plane of from 0 to 5 degrees, said wafers having an averageeffective length of at least 8 inches (200 mm) said lengths of lumberhaving cut edges defined in said panel by cuts extending substantiallylongitudinally of said panel said cuts being spaced defined the width ofsaid lumber.

Preferably said wafers will have a maximum average thickness of 0.15inches (4 mm) and an average width of at least 0.25 inches (6 mm).

Preferably said lumber product will have a substantially uniform densityto thickness profile.

Present invention also relates to a method of making a lumber productcomprising laying up a single layer panel having a thickness of at least1 inch (25 mm) from a plurality of wafers, orienting the longitudinallength of said wafers relative to the longitudinal axis of said panel sothat the mean deviation of the lengths of said wafers to saidlongitudinal axis of said panel measured in the major plane of saidpanel is in the range of 0 to 10 degrees and a mean deviation measuredin a longitudinal plane through said panel perpendicular to said majorplane of from 0 to 5 degrees, said wafers having an average effectivelength of at least 8 inches (200 mm) consolidating said layup of wafersunder heat and pressure to set adhesive coating said wafers andconsolidate said layup into said panel having a substantially uniformdensity to width profile and cutting the panel along spacedlongitudinally extending lines to divide said panel into a plurality ofdiscrete lumber lengths having a width equal to the spacing between saidlongitudinal cuts.

Preferably the consolidating conditions will be controlled to yield apanel having a substantially uniform density to thickness profile.

Preferably the density of the lumber products so produced will be in theorder of 25 lb/ft³ (0.4 g/cm³) through 50 lb/ft³ (0.8 g/cm³). Alsopreferably the density will not deviate more than 3% from the meanthrough the panel thickness.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, objects and advantages will be evident from thefollowing detailed description of the preferred embodiments the presentinvention taken in conjunction with the encompanying drawings in which

FIG. 1 is a schematic plan view of a plan for carrying out the presentinvention.

FIG. 2 is a schematic side elevation of the plan of FIG. 1.

FIG. 3 is a partial plan view of a board or panel constructed inaccordance with the present invention, illustrating the lay of waferstherein.

FIG. 4 is a sectional view along the line 4--4 in FIG. 3.

FIG. 5 is a graph of density versus thickness illustrating a preferreddensity profile with thickness through the board of FIG. 4.

FIG. 6 is a sectional view along line 6--6 in FIG. 4.

DESCRIPTION OF PREFERRED EMBODIMENTS

The term wafer used throughout this disclosure is intended to definewood particles formed by a waferizer as distinct from pulp chips,sawdust, particles or lengths cut directly from a round log or formed byclipping veneer. The size of the sliced wafer used with the presentinvention, particularly the length which is always measured in the fiberdirection, i.e. parallel to the longitudinal axis of the fibers, iscritical to obtaining the required strength to provide a lumber productto replace conventional lumber with a product having essentially thesame strength as the lumber being replaced and without a significantchange in density.

Referring to FIG. 1, adhesive coated wood wafers are brought to thelayup forming equipment via a suitable in-feed device wherein the wafersare relatively uniformly laterally spread and are then fed to anorienting device 12 (see for example U.S. Pat. No. 4,494,919 issued Jan.22, 1985 to Knudson et al) that orients the wafers with theirlongitudinal dimensions substantially aligned as will be described inmore detail here below. In the illustrated arrangement the mat 14 soformed has a substantially uniform density to width profile and iseither layed on a caul plate and transported to a press such as amultiopening press schematically illustrated in 16 or is carried by acontinuous belt or the like to a continuous press 16 and the mat orlayup 14 is pressed and consolidated to form a panel 18, say a panelhaving a total width of 8 feet (2400 mm) and the required thickness(e.g. for nominal 2 inch (50 mm) lumber the consolidated panel must havea 11/2 inch (38 mm) thickness). If a continuous press 16 is used panel18 is continuously moved from the press 16 in the direction of arrow 20,i.e. in the longitudinal direction of the wafers which is the directionin which the wood fibers are aligned in the wafer, into the cuttingstation 22. If the press 16 is not a continuous press, i.e. is amultiopening press or the like the mat 14 is carried on a caul plate tobe consolidated into a panel, the panel will be withdrawn as indicatedby arrow 20, separated from their respective caul plates (not shown) andfed one following the other in the direction of the arrow 20, i.e. withthe length of the wafers aligned with the arrow 20 into cutting station22.

Cutting station 22 as schematically illustrated is made up of aplurality of spaced circular saws or cutters 24 axially moveably mountedvia hubs 26 on a shaft 28. Hubs 26 are mounted in a conventional mannerto be driven by the shaft 28 and yet slidable axially on shaft 28 sothat the position of the saws 24 may be adjusted thereby adjust thewidth of the spaces between the saws which determines the width asindicated by the dimensions W1, W2, W3, etc., of the lumber products 30formed from panel 18 (which may be any appropriate width). FIG. 2further provides a schematic illustration of an automatic spacing deviceadapted to adjust spacing between saws 24 including a yoke 32 thatengages its respective hub 26 and is moved along a shaft 34 by asuitable drive bar 36. There will be one drive bar 36 for each yoke 32and one yoke 32 for each of the blades 24 to in known manner adjust theposition of the saw 24 along the shaft 28. Generally the spacing of thesaws or cutters 24, i.e. widths W1, W2, etc, will be greater than thethickness T of the panel.

The two outermost blades, i.e. the top and bottom blade 24 in FIG. 1 areused to trim the panel 18 and provide trimmed strips as indicated at 38.

A suitable cut off saw schematically indicated at 40 traverses the panel18 after the appropriate length of cut boards 30 has passed the saws 24to cut the boards off to the required lengths. In continuous operationthe saw 40 will move both transversely and longitudinally so that asquare cut is provided across the width the panel 18 (see the arrows 42and 44 in FIG. 1) and where discrete panels 18 are formed on caul platesthe cut off saw may not be necessary but may be useful for trimming tolength.

It is intended that press 16 be operated as above indicated to provide apanel 18 of adequate strength which requires that wafers having at leastan average length of about 8 inches (200 mm) (length is alwaysconsidered as measured in direction of the grain of the wafer)preferably an average length of 10 to 24 inches (250-600 mm) be used.Normally such wafers will be cut at an average thickness not exceeding0.15 inches (4 mm), preferably less than 0.1 inches (2.5 mm) with thethicker wafers normally being used to produce the thicker panel. Thewafers will preferably have an average width of at least 0.25 inches (6mm), more preferably at least 0.5 inches (12 mm) and in many cases willhave a width to thickness ratio of over about 10.

The wafers must be oriented with their length direction aligned relativeto the longitudinal direction of the lumber which as above indicated isformed by cutting substantially parallel to the longitudinal directionof the panel 18 or parallel to the direction of outfeed from the press16. This orientation will never be 100% in the machine direction, i.e.parallel to the longitudinal axis of the panel 18 and the axial lengthof the lumber products 30, but will be such that the mean deviation ofthe wafer lengths (fiber direction) from the longitudinal axis of thepanel 18 and thus form the longitudinal axis of the lumber product iswithin the range of approximately 0 to 10 degrees when measured in themajor plane of the panel 18, i.e. measured on say the upper surface ofthe panel 18 as indicated at 46 in FIGS. 2 and 3. The mean deviationmeasured in a plane extending longitudinally to the panel 18 or boards30 say parallel to the cut faces formed by the saws 24 (i.e.perpendicular to the plane 46) will normally be in the range of 0 to 5degrees as schematically illustrated by the angle A in FIG. 4. The angleA will preferably be small closer to the 0 to 3 degrees since if theangle A is too large and wafers extend almost from one major surface ofthe panel to the other, a weak product will be produced and this must beavoided.

Press cycle will be controlled (including the rate of change oftemperature assuming a continuous press) depending on the product to beproduced but normally will be such that the density to thickness profileis substantially constant, i.e. a deviation of less than 3% from themean for a normal lumber product. Generally the faces of the panel 18contacting the press plates will have a slightly higher density than thecentral portion of the panels. If the lumber product is to be used asplanking, i.e. with the loading perpendicular to the major face, it maybe desirable to manufacture a panel with distinct core and surfacelayers with the surface layers having a significantly higher densitythan in the core. With a plank the deviation in density from the meanmay be as high as 10% depending on the relative thickness of the densesurface layers to the less dense core portion.

The uniform profile of density to thickness is significantly moreimportant with the structural lumber product of the present inventionwhich will normally be loaded perpendicular to its cut or edge face,i.e. parallel to the face represented by surface 46 of panel 18 so thatthe major faces of the panel which contact the platens of the press willbe aligned with the load and the center or core of the panel no longerforms the neutral axis when the structural member is being stressed.

In the operation of the present invention suitable wafers as abovedescribed are first formed in a mat 14 of approximately 4 times thedesired finished thickness of the panel 18 which will normally limit themaximum thickness of the panel to about 4 inches (100 mm). The waferswill be precoated with adhesive normally a phenol formaldehyde resinalthough isocyanates may also be used or any other suitable adhesive.Normally if phenol formaldehyde is used a dried powdered resin will beused although with proper application a wet or liquid resin may also beused. Change in resin may require a change in the pressing schedule toensure proper curing of the resin when the mat is under pressure.

Assuming the lumber to be produced is nominal 2 inch 50 mm) thick lumberthen the thickness of the panel 18 will be 11/2 inch (40 mm) and thecutters 24 will be separated to cut the panel 18 into strips and toproduce a 2×6; 2×8; 2×10; 2×12; or even 2×16 inch; etc, lumber asdesired. Generally the wider the width dimension the more valuable theproduct yet it is as easy to manufacture a 2×16 inch board as it is tomanufacture a 2×4 utilizing the present invention and any desiredproduct mix may be made. Furthermore, if a continuous press is used thelength of the boards so formed is determined simply by activation of thecutoff saw 40 to cut the boards to the desired length. If caul platesare used the saw 40 may simply be used to trim the lumber to length oralternatively it could be trimmed at some other stage. In this case themaximum length is determined by the length of the caul plate.

EXAMPLE 1

A single layer oriented wafer mat was hand felted aspen wafers onto an 8foot (2400 mm) long caul plate. The wafers used were 12 inches long and0.025 inches (0.6 mm) thick and 11/4 inch (30 mm) wide and were producedat MacMillan Bloedel's Thunder Bay Division. 5% powder phenolformaldehyde resin and 2% slack wax were applied to the wafers. Amatching 8 foot caul plate was placed on top of the mat before pressing.The felted wafer mat was then advanced through a hot press (in theResearch Centre under lab conditions) in 2 foot stages. Each stage waspressed for 20 minutes at a press temperature of 210° C. The resultingproduct had a thickness of 11/2 inches and an average density of 40lb/ft³ (0.64 grams/cc). The modulus of elasticity (MOE) of the sectionso produced was 1,697,000 psi (11.70 GPa) measured while applying forcesparallel to the faces formed by the caul plates, i.e. in a directionequivalent to perpendicular to the cut faces of the lumber product.

It will be apparent that the pressing of this sample was not under idealconditions so that the panel produced was far from ideal. However thesample clearly indicates that the modulus of elasticity (MOE) is atleast equivalent to that for conventional lumber of the grade specifiedand at a reasonable density.

EXAMPLE 2

In a further attempt to determine the applicability of utilizing wafersthat are relatively inexpensive, a relatively thin aspen veneer 0.05inch (1 mm) thick at 10% moisture content was clipped to 12 inch lengthby 1/2 inch width strips to make an 8 foot long, 11 inch wide by 21/2inch thick oriented lumber billet utilizing a continuous press,microwave heating, 6% powdered phenol formaldehyde resin and 2% slackwax. A mat was formed from wafers precoated with adhesive and orientedto substantially align with the length of the lumber product and passedthrough the press over a period of 9 minutes. The actual .[.specificgravity.]. .Iadd.density .Iaddend.of the resultant lumber was .[.46.]..Iadd.40 .Iaddend.lb/ft³ (0.64 grams/cc) at 12% moisture and theresulting board had an average MOE of 1,650,000 psi and a modulus ofrupture (MOR) of 6900 psi.

Another board made in a similar manner had a specific gravity of 39lb/ft³ (0.54 g/cc), a MOE of 1,500,000 psi and a MOR of 5,500 psi.

Examples 1 and 2 clearly demonstrate that it is practical to manufacturelumber products having acceptable physical characteristics forstructural lumber applications when made from a species such as aspenwhich is not a good species for such materials and at a final densitythat while higher than aspen is similar to that of many species.

Having described the invention modifications will be evident to thoseskilled in the art without departing from the spirit of the invention asdefined in the appended claims.

What is claimed is:
 1. A waferboard lumber product comprising discretelengths of lumber each having a thickness of at least 1 inch (25 mm) andbeing cut from a single layer panel made from wood wafers .Iadd.havingan average thickness as cut by a waferizer of less than 0.05 inches(1.25 mm) and an average width of greater than 0.5 inches (12.5 mm), anda width to thickness ratio of at least 10 to 1, substantially all of.Iaddend.said wafers having been oriented with their lengths having amean deviation to the longitudinal axis of the panel measured in themajor plane of said single layer panel in the range of 0 to 10 degreesand a mean deviation measured in a minor plane extending longitudinallyof said panel and perpendicular to said major plane of from 0 to 5degrees, said wafers having an average length measured in the graindirection of the wafer of at least 8 inches (200 mm), said discretelengths of lumber each having a pair of cut edges spaced to define thewidth of said lumber products said cut edges extending substantiallyparallel to said longitudinal axis of said panel from which said lumberis cut.Iadd., said lumber product having an MOE of at least 1,500,000psi at a density of 40 lb. per cubic foot.Iaddend..
 2. A lumber productas defined in claim 1 wherein said lumber product has a density withinthe range of 25-50 lb/ft³. .[.3. A lumber product as defined in claim 2wherein said wafers have an average thickness of less than 0.15 inches(4 mm) and an average width of at least 0.25 inches (6 mm)..].
 4. Alumber product as defined in claim 2 wherein said mean deviationmeasured in said minor plane is in the range of 0 to 3 degrees . .[.5. Alumber product as defined in claim 2 wherein said average width is atleast 0.5 inches..].
 6. A lumber product as defined in claim 2 whereinsaid wafers have a mean length of between 10 and 24 inches (250-600 mm).A lumber product as defined in claim 2 having a substantially uniformdensity to thickness profile.
 8. A lumber product as defined in claim 2wherein said density profile to thickness has a deviation from the meandensity of less than 3%. .[.9. A lumber product as defined in claim 3wherein said wafers have an average thickness of less than 0.1 inches(2.5 mm)..].